Multipath I/O

From multi-pathing is when it is possible for a server to achieve the same disk subsystem across multiple host bus adapters. Especially in clustered environments, this technology is widely used and brings the redundancy required.

Modes of operation

Active / Passive

If an active path, for example by a hardware failure, the data transfer over the still existing connections can continue to take place ( failover ) the application running on the system possibly affect programs without.

Active / Active

The data transfer between two systems may utilize all available data paths are distributed ( load balancing). Through the use of multiple host bus adapter in the disk subsystems and servers thus the possible total transmission rate can be increased. Again, take in an error, the compounds still present in case of failure of a path whose ongoing data transfers.

Implementations

There are several approaches to implement multi-pathing:

• In the Logical Volume Manager a physical volume can be configured with multiple paths ( for example, on HP- UX with PV links)
• In the block layer, for example, Linux in the Device Mapper
• The driver of the host bus adapter ( for example, in the QLogic driver for Linux)
• The drivers for hard disks ( for example, on AIX MPIO )
• Makes visible as an additional driver, the new virtual disks for the operating system ( for example EMC Power Path with Power Devices)

• Memory technology
• IT architecture